package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.RedisData;
import com.hmdp.utils.RedisService;
import io.netty.util.internal.StringUtil;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private RedisService redisService;

    @Override
    public Object queryById(Long id) {
        //缓存穿透
       // Shop shop = queryWithMutex(id);
        //互斥锁解决缓存击穿
       //逻辑过期解决缓存击穿问题
       // Shop shop = queryWithLogicalExpire(id);
        //TODO 封装成工具类解决缓存穿透问题
      //  Shop shop = redisService.queryWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //TODO 封装成工具类解决缓存击穿问题
        Shop shop = redisService.queryWithLogicalExpire(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);
        if (shop == null) {
            return Result.fail("店铺不存在！");
        }
        return Result.ok(shop);
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺id不能为空");
        }
        //1.更新数据库
        updateById(shop);
        //2.删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + shop.getId());
        return Result.ok();
    }

    public Shop queryWithMutex(Long id){
        //TODO 1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
        //TODO 2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //TODO 3.存在，直接返回（缓存命中）
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中的是否为空值
        if (shopJson != null){
            //返回错误信息
            return  null;
        }
        //实现缓存重建

        //TODO 4.redis中不存在，根据id查数据库，没有则返回错误
        //TODO 获取互斥锁
        String lockKey = "lock:shop:"+id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            if (!isLock) {
                //失败，则休眠重试
                Thread.sleep(50);
              return   queryWithMutex(id);
            }
            //判断是否获取成功

            //成功 根据id查数据库
            shop = getById(id);
            //模拟重建的延时
            Thread.sleep(200);
            if (shop == null) {
                //1.（解决缓存穿透）将空值写入redis
                stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, "",CACHE_NULL_TTL, TimeUnit.MINUTES);
                //2.返回错误信息
                return null;
            }
            //TODO 5.有则写入redis
            stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //TODO 释放互斥锁
            unlock(lockKey);
        }

        //TODO 6.返回
        return shop;
    }
    public Shop queryWithLogicalExpire(Long id){
        //TODO 1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
        //TODO 2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            //TODO 3.不存在，直接返回（缓存未命中）
            return null;
        }
        //TODO 4.redis中存在，json反序列化成对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data =(JSONObject)redisData.getData();
        Shop shop = JSONUtil.toBean(data, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //未过期 返回店铺信息
            return shop;
        }
        //已过期 缓存重建（获取互斥锁，判断是否获取锁成功）
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        if (isLock){
            //TODO 成功，开启独立线程实现缓存重建 返回过期店铺信息
            CACHE_REBUILD_EXECUTOR.submit(()->{
                //重建缓存
                try {
                    this.saveShop2Redis(id,20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
         return shop;
        }


        //失败，直接返回过期店铺信息


        //TODO 6.返回过期店铺信息
        return shop;
    }
    public Shop queryWithPassThrough(Long id){
        //TODO 1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
        //TODO 2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //TODO 3.存在，直接返回（缓存命中）
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中的是否为空值
        if (shopJson != null){
            //返回错误信息
            Result.fail("店铺信息不存在");
        }

        //TODO 4.redis中不存在，根据id查数据库，没有则返回错误
        Shop shop = getById(id);
        if (shop == null) {
            //1.（解决缓存穿透）将空值写入redis
            stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, "",CACHE_NULL_TTL, TimeUnit.MINUTES);
            //2.返回错误信息
            return null;
        }
        //TODO 5.有则写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //TODO 6.返回
        return shop;
    }
    public void saveShop2Redis(Long id, Long expireSeconds) throws InterruptedException {
        //1.查询店铺数据
        Shop shop = getById(id);
        Thread.sleep(200);
        //2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusMinutes(expireSeconds));
        //3.写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key,"1",10,TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
}
